My experience of Nautilus 2 is a little out of date (about 4 years) - so may be inaccurate. But to try & help you - here it is....
The vessel itself is wonderful. The largest lob I have been on. Huge cabins, huge en-suites & enormous lounge/dining area. The food was also excellent. Good boat crew.
The diving set up was not my favourite, however. They only had 1 1/2 DM for 20+ guests. Also the dhoni was no where near the standard of the lob. Crucially it only had 2 cramped exits (jump points). The shortage of DMs & the time it took everyone to jump from the dhoni meant that dropping the group into current did not work at all well.
Consequently, we only did the 'pretty' sites & omitted the 'high energy' sites. So not much in the way of pelagics on view. Also the compressor only did 180 bar fills - so short dives.
I hope they have fixed the dive operation over the intervening years. If so, it would be a wonderful lob.
Cheers
John